5. A cipher processes the input one block of elements at a time, producing an output block for each input block, whereas a stream cipher processes the input elements continuously producing output one element at a time. . Two alternatives to DES are AES and 7. DES reas of concern regarding the level of security provided by DES are the nature of the algorithm and the attack exploits the fact that an encryption m often takes slightly different amounts of time 8. or decryption al on different inputs. cryptography is asymmetric, i ate keys, in contrast to involving the use of two encryption, which uses only one key ved by a cryptographic algorithm applie to a small block that to a smail cryptographic algorithm applied to the message ock of data that is a function of the message. e ender 'signs a message with ts private keyt sening ssage with its private key. Signing iB " is a description of a